docs: restructuring the README.md

[leogr]

Signed-off-by: Leonardo Grasso me@leonardograsso.com

What type of PR is this?

Uncomment one (or more) /kind <> lines:

/kind bug

/kind cleanup

/kind design

/kind documentation

/kind failing-test

/kind feature

Any specific area of the project related to this PR?

Uncomment one (or more) /area <> lines:

/area build

/area plugin-sdk

/area tests

What this PR does / why we need it:

Just a restructured README.md.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

[poiana]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jasondellaluce, leogr

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